Recording machines and adapters are available for recording onto and playing back from magnetic strips on cards or photographs that either move along a slot in the recorder or are tracked by a moving magnetic head within the recorder. Magnetic strips on cards and photographs allow recordings of a few seconds in length and are useful for brief comments or messages and for many educational applications.
In some circumstances, it is desirable to have a prerecorded message that cannot be erased or recorded over, and this is especially useful where a pre-recorded question, instruction, pronunciation, example, etc. is recorded on an instruction portion of a card, and another portion of the same card is reserved for a student response or imitation. The pre-recorded portion must not be erased or recorded over if the card is to be used over and over by a succession of students. One previous way of doing this was to use more than one recording strip on a card so that one magnetic strip was reserved for instructional purposes and another was used and reused by students. This complicates the recorder and requires capacity to track two different magnetic strips in the same device.
Recent innovations in the art of recording onto and playing back from magnetic strips on cards or photographs have produced a much slower tracking speed allowing much longer messages to be recorded and played back from a single magnetic strip of ordinary length. This makes it feasible for a portion of a single magnetic strip to be reserved for instructional messages and another portion of the same strip to be used repeatedly by students, but it also requires some system for preventing accidental erasure of the pre-recorded instructional portion.
The invention involves recognition of a simple and economical way that any selected portion of a magnetic recording strip on a card or photograph can be protected from accidental erasure or re-recording to preserve the pre-recorded material. The invention aims at simplicity, economy, reliability, and ease of operation in insuring that any desired portion of a magnetic recording strip not be erased or recorded over and only predetermined portions of any magnetic strip can be recorded on.